BACKGROUND: Transsphenoidal surgery guided by intraoperative MRI (iMRI) is related to higher rates of tumour resection. The influence of iMRI on endocrinological outcome is still unclear. This study evaluates the endocrinological outcome of iMRI-guided transsphenoidal surgery. METHODS: A series of 60 patients operated by iMRI-guidance for inactive adenomas were matched to a previous series of 32 controls. The following factors were used for matching: gender; age; tumour volume; Hardy's grade; pituitary function; pituitary stalk configuration; stalk effect hyperprolactinemia; arterial hypertension; diabetes mellitus; smoking. RESULTS: Total resection rates were higher in the iMRI group (85%) than in the control group (69%). Follow-up times were 3.2 ± 1.0 years in the iMRI group and 6.8 ± 4.1 years for controls. No patient in the iMRI group needed additional tumour treatment, as opposed to 13% of the controls. The rate of postoperative hypopituitarism was 29% in the iMRI and 45% in the control group. Predictors for new hypopituitarism in the iMRI group were age >65 years, Hardy's grade >2 tumours and hypertension. Recovery rates were 59% in the iMRI and 45% for controls. Predictors of better recovery rates were female gender and age <65 years. The following predictors lead to an endocrinological benefit of iMRI-guidance: Hardy's grade <3 tumours; age <65 years; no hypertension; non-smokers; dysfunction of two or three axes pre-operatively. CONCLUSION: The use of iMRI in transsphenoidal surgery for non-functioning pituitary adenoma might lead to higher total resection rates. In our series, resection of remnants detected by iMRI was neither associated with higher incidences of postoperative hypopituitarism nor with lower recovery rates of pituitary axes.